The present invention relates to a phase-contrast haploscope used to examine various functions of binocular vision, i.e. subjective angle of squint, retinal correspondence, fusion faculty, subjective vision, suppression, aniseikonia, circumflex deviation and others, by separating images of right and left eyes in environment most similar to ordinary vision.
According to The Medical Dictionary issued by Nanzando Co., Ltd., a haploscope is an optic axis measuring instrument, which forms images of two separate targets which are similar to or identical to each other on both eyegrounds using a prism or reflecting mirror for uniting the images by the capability of binocular vision and examines fusion power, fusional motion, and the relation between adaptation control and convergence from the capability of binocular vision.
As shown in FIG. 12, in a conventional synchronous type phase-contrast haploscope which has been practically used, targets g, h of eyes are separated by using a pair of sectors a, b which correspond to right and left eyes and which rotate at a high speed in front of eyes with an inter-hole phase difference of 90 degrees and a pair of right- and left-hand projectors e, f having sectors c, d which are synchronized with the sectors a, b, respectively (an image projected by the right-hand projector e is seen only by the right eye, and an image projected by the left-hand projector f is seen only by the left eye). In the FIGS., i to l denote rotating motors, m denotes the plane of projection, n and o denote left- and right-hand lantern slides, p denotes an examinee, and q and r denote left- and right-hand projecting beams.
Because of a rotating speed (100-120 c/s) higher than a critical fusion frequency, in a subjective sense, both targets g, h are recognized continuously and concurrently. By using such apparatus, it is possible to examine said various functions of binocular vision under conditions quite similar to ordinary vision.
On the other hand, there exists a liquid crystal phase-contrast haploscope. The flashing frequency of an image can range from 0.1 to 50 c/s by using liquid crystal shutters which are synchronized with changeover shutters for both eyes. Also, the liquid crystal shutter has an opening/closing characteristic which provides an operation speed up to 50 c/s with a rise/fall time of 5 ms.